Microbial technique to treat recycled aggregates from construction waste for its effective reutilization in concrete

Excessive consumption of natural resources for concrete production results in the diminution of conventional resources, leading to the scarcity of construction materials. Perhaps, the dumping of construction wastes increases disposal problems. Nevertheless, the requirement for aggregates in the construction sector increases. The recycling of construction waste to produce recycled coarse aggregate (RCA) as a suitable alternative to natural coarse aggregates (NCA) conserves natural resources and promotes sustainability in construction. However, the quality of recycled coarse aggregate was inferior compared to natural coarse aggregates due to the adherence of mortar. This paper investigates the sustainable use of Bacillus subtilis with different concentrations to enhance the quality of RCA. The concrete mixes manufactured with optimized bio-deposited recycled coarse aggregate (BRCA) were tested for their mechanical and durability properties. It could be observed that the strength of bio-deposited recycled aggregate concrete (BRAC) was enhanced by 12.63% relative to normal aggregate concrete (NAC), and the durability properties such as water absorption, chloride penetration and carbonation of BRAC were reduced by 18.53%, 16.52% and 20% relative to recycled aggregate concrete (RAC). Microstructural studies through SEM and XRD revealed the deposition of CaCO3 on the micro-pores of RCA, and that improves the properties of the concrete.